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Overburden 'IhicJQwss: Varying frrm approximately 1000 to 2100 feet. <br />• Mining Height: 9-11 feet on advance. <br />Roof: Comprised of mudstones aryl sarrlstones with intermittent sandstone <br />channels. Tap coal of 2-3 feet in thic3mess was left on the roof. Mesh <br />used in localized areas to maintain intersections, repair fall areas. <br />Pillaz widths ~*+~-~-~~ at crosscut 39 to enhance roof and rib stability <br />as cover increased. <br />Ribs: Rib sloughage was moderate to severe and increasing with increasing depth. <br />Floor: 'Ihe lower "D" seam was used as floor which provided ca~etent wrclitions. <br />Anomalous Conditions: Increased rib inLStability associated with increasing <br />cover depths. Typical intermittent seeps fr®n both roof <br />arcs floor associated with sardstane channels encountered <br />at various locations. Roof fall on belt line between <br />cross cuts 35 and 36 necessitated withdrawal from this <br />panel. No retreat mining occurred in Panel Y during <br />1993. <br />Subsidence Eapacts 1993 <br />Cypnls Orchard Valley Coal Corporation conq~leted advance development and partial <br />floor extraction on retreat in Panel C, advance development arri full pillaz <br />• extraction of Panel AA and the western extreme of the II West Sukmains, advance <br />development of Panel Z, advance development of Panel Y, aryl the advance <br />development on the North Mains Bypass reconnecting the Orchard Valley Fast aryl <br />West mines. Subsidence survey monitoring of selected wide-spaced rrornmients in <br />the vicinity of active mine workings was conducted during October and DeoPmbex, <br />1993, and January, 1994. Surveying of these selected stations was conducted in <br />accordance with the projected monitoring addressed in the 1992 Annual Subsidence <br />Report with the exception that station 6 was again surveyed to provide control <br />for the Pitkin Mesa Pipeline survey. Selected subsidence monitoring stations <br />established over the Pitkin Mesa Pipeline were monitored in May and October, <br />1993. <br />wide-Spaced Monitorirxx GYid Station Suamnarv <br />Fourteen wide-spaced monitoring grid stations were surveyed for the 1993 <br />reporting year. Stations 6, 14, 15, 16, and 95; drill holes 55, 65, 66, aryl 68; <br />and subsidence points 94, 96, 97, 98, and 99 as depicted on Map No. 2-5 were <br />surveyed. The following discussions present a station by station assessment of <br />survey results generated for 1993. Monitoring station data sheets are appercied <br />to this report for reference. <br />Station 6: Surveys were initiated in August 1982 and continued biannually <br />through July 1984. Surveys were reinitiated in 1987 arcl <br />conducted annually through 1993. Station 6 is located on <br />• approximately 350 feet of overburden and lies approximately <br />300 feet north of the 1st North, 2 1/2 West panel retreat <br />mined from May through June, 1983. Station 6 lies adjacent to <br />the II West Submain development advanced in 1987. October <br />